Environmental geology of the Russellville, Arkansas area

Abstract

The natural environment imposes fundamental limitations on the uses of certain areas by man. Therefore, the factors that make up the natural environment must be the subjects of early and thorough studies in an area where urbanization is occurring. All indicators show that Russellville, Arkansas is such an area.

The study area is located in Pope County, Arkansas, 75 mi west of Little Rock in the Arkansas River Valley physiographic province.

In order to develop a more complete understanding of the geologic setting of the area and to evaluate the implications that geology could have for urban planning, 8 basic maps were prepared. These maps deal with areal geology, mineral resources, thickness of sand and gravel deposits, topographic slopes, areas of potential flooding, surficial materials and depths to bedrock, construction properties of soils, and land-use planning.

Sedimentary rocks of the Pennsylvanian System and unlithified sediments of the Quaternary System crop out in the Russellville area. Pennsylvanian rocks consist of the Atoka Formation, the Hartshorne Sandstone, and the McAlester Formation. The Quaternary deposits consist of stream and river terrace alluvium deposited during the Pleistocene Epoch and river alluvium of Recent age.

Rocks of the area are folded into a series of plunging east-west trending anticlines and synclines, which have been deeply eroded. Generally, the folds are nearly symmetrical with limbs that dip about 5 to 8 deg. The southern limb of the Shinn syncline, however, dips about 80 deg. The strata are jointed with as many as 3 joint sets being fairly common. Two east-west-trending faults are known in the area.

A mineral-resources map shows the locations of potential resource recovery areas, not including oil or gas. Sand is abundant in the Arkansas River channel and flood plain. Sandstone also is plentiful and is quarried from several areas in the Hartshorne Sandstone. Coal reserves are located in the Ouita and Shinn basins, however only the Shinn basin deposts are recoverable at the present time because Ouita basin has been flooded by the Dardanelle Reservoir. Ground water is available from the sediments of the Arkansas River flood plain. Another source of ground water is available from the Pennsylvanian bedrock for domestic water supplies.

On the topographic slope map, relief has been converted into percent of grade. These values have been categorized and mapped by symbols. Most of the area is in grades which range from 0 to 7 percent. Generally, slope will present no problems in the development of these tracts. However, grades in excess of 15 percent are present on the escarpments of Norristown and Carrion Crow Mountains, the hogback ridge of the Shinn basic, and the dip-slope of the Pleasant View Mountain.

The potential flooding and drainage map shows areas that the U.S. Army Corps of Engineers includes within the "100-yr" flood plain. Drainage systems and basins are also outlined on the map. The areas most likely to flood are: (1) adjacent to the Arkansas River downstream from the Dardanelle Dam, (2) within the lower part of the Whig Creek drainage basin, (3) along Prairie Creek within the city of Russellville and south of the Russellville Dike, and (4) downstream from the Russellville waterworks dam on the Illinois Bayou.

Types and thicknesses of flood plain alluvium, terrace alluvium, colluvium, and residual soil are shown on the surficial geology map. Extensive deposits of alluvium lie within the Arkansas River flood plain where alluvium may be as thick as about 55 ft at some places. Terrace alluvium covers approximately one-third of the study area with deposits which may be as thick as about 30 ft. Residual soil is present as a mantle overlying bedrock where grades are less than about 8 percent. Colluvium may be present because of soil creep where grades are greater than about 8 percent. Colluvium is located beneath escarpments and along the base of hogbacks, especially where the Hartshorne Sandstone crops out as a ledge above the shale, siltstone, and sandstone of the Atoka Formation. Generally, these colluvial areas are likely to cause site development problems.

The map of construction properties of soils provides a quick reference to the properties of soil that are significant in construction work. The following information is included in the explanation on the map: soil description, parent material of soil, drainage, permeability, shrink-swell potential, plasticity, and acidity.

The land-use map shows proposed uses for tracts within the Russellville area, including these categories of- land: (1) commercial, (2) flood easement, (3) industrial, (4) public, (5) residential (low-, medium-, and high-density), (6) resource recovery, (7) scenic vista, recreation, or park land, and (8) undeveloped land.(slopes or 4 agricultural land). The maps and information included within the study are designed to be used for regional planning only. They should not be used for detailed site planning. Additional studies will be necessary, for specific development projects.